DNA, RNA And Genes

Question 1

What cellular processes involve DNA?

Answer 1

• Replication
• Transcription/Translation
• Viruses

Question 2

What cellular processes involve RNA?

Answer 2

• Translation
• Replication
• Transcription
• Viruses
• Regulation for gene expression

Question 3

What cellular processes involve nucleotides?

Answer 3

• DNA synthesis (replication)
• RNA synthesis (replication)
• Repair mechanisms
• Recombination
• Transcription

Question 4

Can you recognise whether a nucleotide is a dNTP or an NTP from the structure?

Answer 4

NTP -> nucleoside triphosphate -> contains a nucleoside bound to three phosphates

• Nucleoside (base + sugar)
• Nucleotide (base + sugar + phosphate)

dNTP -> nucleoside triphosphates containing deoxyribose (dATP - deoxyadenosine triphosphate)
ATP -> adenosine triphosphate

Question 5

What is a pyrimidine and what is a purine?

Answer 5

Pyrimidine -> three rings -> C and T

Purines -> two rings -> A and G

Question 6

What are the base pairings found in DNA and RNA?

Answer 6

A pairs with T

C pairs with G

Question 7

Why is the DNA always the same width?

Answer 7

Adenine is a purine and has two rings -> pairs with thymine which is a pyrimidine and has three rings

Guanine is a purine and has two rings -> pairs with cytosine which is a pyrimidine and has three rings

Therefore they have the same width

Question 8

What is the general structure of DNA?

Answer 8

Contains a base, sugar (pentose or ribose), and a phosphate group

5’ phosphate group
3’ hydroxyl group
Synthesised 5’ to 3’

Question 9

Which of the base pairings is stronger and why?

Answer 9

There are two hydrogen bonds between A and T
There are three hydrogen bonds between G and C

The bond between G and C is therefore stronger

Question 10

What is the type of chemical bond that exists between the phosphate and the pentose of the neighbouring nucleotide?

Answer 10

Strong covalent bonds form between the phosphate group and two 5-carbon ring carbohydrates (pentoses) over two ester bonds. A phosphodiester bond ->a covalent bond is formed between the 5’ phosphate group of one nucleotide and the 3’ OH group of another

Question 11

What is the type of chemical bond that exists between the base pairing nucleotides?

Answer 11

Hydrogen bonding

Question 12

What does it mean that DNA is anti parallel?

Answer 12

Runs in the opposite direction -> the strands

Question 13

Why was the discovery of the structure of DNA central to our understanding of inheritance?

Answer 13

It was known that chromosomes are the unit of inheritance but they couldn’t determine the structure of DNA - why is DNA a better candidate for the genetic material than proteins?

• More stable
• Only found in chromosomes
• Used as a scaffold
• 4 nucleotide bases

Proteins

• Unstable
• Found in other parts of the cell
• Directly responsible for the phenotype
• Enzymatic activity

Question 14

What is different about the tertiary structures of DNA and RNA?

Answer 14

RNA can form complex 3D structures
RNA can bend back on itself

There are three possible structures of DNA - A, B and Z
Naturally DNA is in the right handed form
Possible for DNA to form hairpin structures

Question 15

What are the major and minor grooves in DNA?

Answer 15

Are important in the attachment of DNA Binding Proteins involved in replication and transcription

Major groove - occurs when the backbones are far apart - DNA binding proteins interact with the bases on the major groove side
Minor groove - close together

Question 16

In what phase of the cell cycle does DNA replication occur?

Answer 16

The S phase

Question 17

Which of the DNA polymerases are involved in DNA replication and which is the main one?

Answer 17

There are five DNA polymerases but only two of them are involved in DNA replication - DNA Polymerase III and DNA Polymerase I
DNA Polymerase III - main polymerase in DNA replication
DNA Polymerase I - functions in repair and recombination too